1. Field of the Invention
The invention relates to an apparatus for identifying, in an interlaced video recording, the frames of an original cine-film sequence from which the video recording has been derived.
The invention also relates to a video rate convertor including such an apparatus, and to a motion picture encoder.
When a cine film has been transferred to a video recording (by a so-called telecine operation), the differences between film and video standards generally do not permit a simple 1:1 correspondence between video frames and film frames. This is particularly true in view of the interlaced character of most video formats, whereby the odd-numbered picture lines and the even-numbered picture lines of each frame are transmitted in two separate fields. Even where a regular pattern of correspondence exists, in theory, it 15 can be unknown, or it can become disrupted by subsequent editing operations performed in the video domain.
2. Description of the Related Art
The inventors have recognized that for many applications, it would be advantageous to have an apparatus which could identify and perhaps reconstruct the original film frames from the fields of the video recording.
A very important application of such a technique might be in data compression video encoding systems, such as the MPEG system standardized by ISO. Such systems exploit the high degree of coherence both within and between successive frames of a motion picture sequence To eliminate redundant information while maintaining a good subjective picture quality. If the sequence being encoded is a video recording made by telecine, the frames encoded might be a mixture of fields taken from different film frames, which lack the coherence that was present in the original frame. The output quality of the encoder is thus seriously reduced.
Another possible application of the proposed apparatus may be suggested by WO 92/09172, which describes a display system including interpolation of additional lines between the lines of interlaced video fields. The system described therein operates in different modes depending on whether the original picture source is a video source or a telecine source. Unfortunately, the only solution proposed in WO 92/09172 relies on flag signals being generated by the telecine machine and included in the video signal to indicate whether the source is a video camera or telecine. Of course a vast number of films have already been transferred to video without these special flag signals, and it will not be practical to return to the original film source in most cases.